Process of bleaching paper-pulp and the like.



K. M'O'RCH. PROCESS OF BLEACHING PAPER PULP' AND THE LIKE. APPLICATION FILED NOV. 30, 191 4.

Patented Nov. 16, 1915.

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K. MURCH.

PROCESS OF BLEACHING PAPER PULP AND THE LIKE.

APPLICATION FILED NOV. 30, 19M.

Patented Nov. 16, 1915.

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xms'rorrnn M53011, or GREAAKER, NORWAY.

PROCESS OF BLEACHING PAPER-PULP AND THE LIKE.

Specification of Letters Patent.

Patented Nov. 16, 19115.

Application filed November 30, 1914. Serial No. 874,890.

To all whom it may concern:

Be it known that I, KRIsTorFnR MoRcH, a subject of the King of Norway, residing at Greaaker, Norway, have invented certain new and useful Improvements in the Processes of Bleaching Paper-Pulp and the like; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to letters or figures of reference marked thereon, which form a part of this specification.

This invention relates to the bleaching of pulp and has for its object a process and plant by means of which the bleaching is effected in a more rapid and economical manner than by means of the processes hitherto employed.

It has frequently been pointed out that the bleaching of pulp is effected in the shortest possible time and with the least consumption of bleaching agent when the bleaching'takes place in a strongly concentrated condition. Thus several years ago it has been proposed to bleach in edge runners (icollergangs). This latter method has not however been much used in practice owing to the fact that for a large production an unreasonably large number of mills with a correspondingly high expenditure of power would be required and by reason of the length of treatment the pulp would become slimy and difficult to treat. The only methodof bleaching in a more concentrated condition which appears to have obtained a somewhat extended use is the Dobson method by which the pulp in the form of sheets in a dry orsemi-dry condition in a revoluble and closed drum is mixed with a comparatively concentrated bleaching agent,

which during the revolution of the drum is absorbed into the dry pulp. This process is however subject to the drawback that the vessels employed must be emptied and filled periodically which requires much manual labor and other expenditures, and moreover the process has the drawback that it is not possible to follow the working of the process.

The present invention has now for its object a process which besides having the advantages of the Dobson process enables a continuous working and an accurate control of the proceeding of the bleaching operation. According to this process the pulp is in a comparatively dry condition supplied with bleaching agent which is pressed into the fibers by means of edge runners, kneadlng machines or the like whereupon the pulp so treated is introduced into an agitating apparatus or a series of such apparatus in which it is carried continuously forward while being constantly stirred, the speed of its conveyance through the apparatus and the distance of its travel being suitably regulated in such manner that the bleaching of the pulp is finished when it leaves the stirring apparatus.

A plant suitable for carrying out the process is diagrammatically illustrated in the accompanying drawing, in which Figure 1 shows the arrangement of the various apparatus. Fig. 2 is an axial sectional view of the stirring apparatus.

The following is a description of the working of the plant illustrated, it being understood however that the process may be somewhat modified in various respects according to circumstances.

The pulp is first brought into such a condition as to contain about 2022% of dry substance, whereupon the bleaching agent is added and the pulp then transferred to one or more chasing (edgerunning) mills 1, 2 which work continuously. This is brought about by keeping the discharge ports of the mills open to such a degree that the desired quantity of pulp is constantly retained in the pan. Vhen several chasing mills are employed these are preferably arranged in series as shown in the drawing (Fig. 1). The pulp is worked in the mills only so long as to properly comminute the pulp and to have the bleaching agent worked thoroughly into the fibers.

From the mills the pulp is conveyed continuously into one or more agitating apparatus 3 which in the example illustrated are constructed as large vertical cylinders divided by horizontal floors in a number of chambers one above the other and being provided with a vertical shaft -i (Fig. 2) carrying stirring rods 5 of which there may be for instance four in each story. The stories are provided with discharge openings 6, 7 alternately at the center and at the periphery and the stirrers move the pulp alternately inwardly and outwardly upon the floors. As an example an apparatus of this construction may have a diameter of about 5 meters and being constructed in 6 stories and being able to contain 3000 kg. of dry substance, in layers of'a thickness of about 30 cm. which are moved constantly forward on the floors.

The stirring rods are constructed in such manner that besides conveying the pulp forward they also effect an overturning and airing of the pulp. This brings about a rapid progress in the bleaching.

The advantages of this system over those at present usually employed are shortl as follows: 1. The time required for the bleaching operation is considerably shortened. (For ordinary easily bleached pulp 4 hours will usually be fully suflicient). 2. The quantity of bleaching agentused is reduced.

, 3. Theplant necessary is compendious and cheap. For a production of 10000 tons a year only two chasing mills and two stirring apparatus of 5 m. diameter and 5 stories will be suflicient. 4:. The bleaching goes on continuously, whereby the costs of labor arev reduced to a minimum. 5. The progress of the bleaching may be exactly followed. 6. The bleaching is effected at ordinary temperature.

I claim: 1. Process of bleaching paper pulp and the like which comprises the steps of working the bleaching agent into the pulp by means of kneadinguntil the pulp has absorbed the bleaching agent and then agitating the pulp until the bleaching has reached to the degree desired.

2. The process of bleaching paper pulp and the like which consists in bringing the pulp in a condition in which it contains about -22 per cent. of dry substance, then adding the quantity of bleaching agent necessary for the bleaching operation; subjecting the pulp to kneading and when the bleaching agent has been thoroughly worked into the fibers maintaining the pulp in agitation until the desired degree of bleaching has been reached.

In testimony that I claim the foregoing as my invention, I have signed my name in presence of two subscribing "Witnesses.

KRISTOFFER MoRoH.

\ Witnesses:

M. E. GUTTovRUsEN,

O. F. HANSEN. 

